1. Field of Invention
The present invention relates to a series-resonant inverter-type fluorescent lamp ballast wherein inversion frequency is automatically controlled such as to control the magnitudes of output voltage and output current.
2. Elements of Prior Art
In series-resonant inverter-type fluorescent lamp ballasts, one significant problem is that of controlling the magnitudes of circuit voltages and currents resulting when the output is unloaded. Another significant problem, which relates to both series-resonant and parallel-resonant ballasts, is that of maintaining an acceptably low lamp current crest factor in spite of the relatively large ripple voltages often present on the inverter's B+ voltage. Finally, another significant problem is that of minimizing variations in lamp power resulting from ordinary variations in the magnitude of the inverter's supply voltage.